For flat and thin display devices, liquid-crystal display devices using liquid crystal, and plasma display devices using plasma have been practically used.
A liquid-crystal display device is a display device with backlight for displaying an image by changing the arrangement of liquid crystal molecules by applying voltage to transmit or intercept light from the backlight. And, a plasma display device is a display device for displaying an image by applying voltage to gas enclosed in a substrate to induce plasma state, so that ultraviolet rays generated by energy due to the return from the plasma state to the original state are irradiated to a fluorescence substance so as to obtain visible light.
On the other hand, in recent years, the development of self-luminescence type display devices using organic EL (electroluminescence) elements which themselves emit light when voltage is applied is in progress. When an organic EL element receives energy by electrolysis, its state is changed from the ground state into an excited state, and when the state returns from the excited state to the ground state, differential energy is emitted as light. An organic EL display device is a device for displaying an image by use of the light emitted from such organic EL elements.
Self-luminescence display devices can be configured to be thinner than liquid crystal display devices, because self-luminescence display devices do not need backlight, differently from liquid crystal display devices which need backlight, for the elements themselves emit light. And, because the moving image characteristic, the view angle characteristic, and the colour reproducibility of a self-luminescence display device are superior to those of a liquid crystal display, self-luminescence display devices using organic EL elements attract attention as a next-generation flat thin display device.
Patent Document 1: JP 2005-084353 (A)